1. Field of the Invention
The present invention relates to a method of fabricating an oxide thin film device using laser lift-off and an oxide thin film device fabricated by the same, and more particularly, to a method of fabricating an oxide thin film device using laser lift-off by transferring an oxide thin film transferred on a polymer-based temporary substrate onto a device substrate, without using an interface on which a defective layer formed due to oxygen diffusion upon laser lift-off is formed, and an oxide thin film device fabricated by the method.
2. Discussion of Related Art
With the rapid development of electronic technologies in the past decade, device miniaturization and power consumption reduction are being accelerated. In order to develop new power capable of replacing typical discardable batteries, studies into a piezoelectric substance capable of converting mechanical energy, such as pressure, force, vibration, etc., into electrical energy are being actively conducted.
As a result of the studies, piezoelectric harvesting technology has been developed. Piezoelectric harvesting technology is expected to be able to be developed as self power source for USN (ubiquitous sensor network), a portable device, etc. Also, by fabricating self power sources in the form of a flexible thin film device, diversification and expansion of use of self power sources are expected. Accordingly, requirement for development of a flexible piezoelectric energy harvesting technology is greatly increasing.
A flexible device is fabricated by preparing an organic substrate such as a polymer substrate since the flexible device requires flexibility, and forming an organic thin film as a thin film configuring a functional part on the organic substrate. However, since a functional part implemented as an organic thin film cannot ensure high performance, the functional part of a flexible device needs to be implemented with an inorganic material. In this case, there are difficulties in directly applying a high-temperature growth process for a piezoelectric substance to a flexible substrate which is made of an organic material. Accordingly, a thin film transfer technique of growing a thin film formed with an inorganic material such as an oxide thin film on a growth substrate and then transferring the thin film on an organic substrate is used.
Also, generally, a thin film transfer technique requires a process of separating a substrate after forming layers. In detail, in order to separate a transferred thin film from a donor substrate, the thin film is bonded on an acceptor substrate and then separated from the donor substrate using a laser lift-off process. However, the laser lift-off process has a problem in that the laser makes a defective layer on the surface of a transferred thin film device, and the defective layer may deteriorate device properties.
Korean Published Patent No. 2007-0068530 (Applicant: Samsung Electronics Co., Ltd, Publishing Date: Jul. 2, 2007) discloses a method of fabricating a substrate for an electronic or optoelectronic device using a GaN based semiconductor, comprising the steps of: forming a first epitaxial layer structure made of a group III nitride-based material on a sapphire substrate which is an initial growth substrate; depositing a thick film layer having a thickness of 30 micrometers or more on the first epitaxial layer; removing the sapphire substrate through a laser lift-off scheme; and treating a surface of the first epitaxial layer structure by dry etching the first epitaxial layer structure.
Meanwhile, C. H. Lee et. al. “Use of Laser Lift-off for Flexible Device Applications”, Journal of Applied Physics, 108, 102814 (2010) discloses a method of fabricating a flexible device using a PLZT thin film, comprising the steps of: forming an oxide thin film on a growth substrate; forming an electrode layer on the oxide thin film; bonding a device substrate on the electrode layer; irradiating a laser beam onto the growth substrate to separate the oxide thin film on which the device substrate has been bonded; treating a surface of the separated oxide thin film using an ion milling method; and forming an electrode layer on the oxide thin film to thereby fabricate a thin film device.
The surface treatment method using ion milling and dry etching is to remove a defective layer formed due to oxygen diffusion upon laser lift-off. However, since the method performs etching only with respect to the defective layer, it may cause another defect due to the physical damages of a device thin film so that the thin film loses its own physical properties. Due to this problem, it is difficult to fabricate a thin film device having excellent physical properties. Also, the fabrication process becomes complicated, and selective etching is difficult.
The present inventors have found that the problem caused by the defective layer formed due to oxygen diffusion upon laser lift-off can be resolved by using a method of fabricating an oxide thin film device using laser lift-off by transferring an oxide thin film transferred on a polymer-based temporary substrate onto a device substrate, without using an interface on which a defective layer formed due to oxygen diffusion upon laser lift-off is formed.